1. Field of the Invention
The invention relates to a mowing and mulching system for lawnmowers having a sickle, with multi-blade knives on an engine-driven driving shaft. The blades rotate in a pot-like cover that is open on the bottom side, and adjoined by a central hub part.
2. Prior Art
Mowing and mulching systems for lawnmowers having a mulching effect by crushing the mowed material a number of times are well known.
For example, a lawnmower is shown in German Patent Application No. 4034978 A1. The knives viewed in the direction of rotation, have repelling elements on the longitudinal trailing edges at the ends of the blades of the knife. At the one end of the blade, these repelling elements project upwards beyond the plane of the knife, and downwards at the other end of the blade. These repelling elements can be produced by turning the edge of the back of the knife up, or by attaching material strips by welding. In addition to end disks that act as repelling elements, repelling elements serve as transport elements that transport the cut, mowed material several times into the range of action of the knife blades as the blades continuously revolve. This subjects the cut material to repeated crushing before the material drops into the pot-like cover, and is re-introduced into the soil.
However, with such a sickle-type mower, the desired mulching effect is inadequately obtained because the repelling elements are not capable of satisfying the purpose for which they are intended.
Therefore, European Patent Application No. EP 0 300 642 A1 and German Patent Application No. DE-PS 19 52 8832 are designed to solve the problem of complete crushing of the cut, mowed material, as well as mulching more efficiently by changing the shape of the knives, as shown in European Patent Application No. EP 0 300 642 A1 and German Patent Application No. DE-PS 19 52 8832 C2.
The mulching lawnmower proposed by German Patent Application No. DE 19 54 2860 A1, contains a mowing knife and two mulching knives arranged one on top of the other and rotate about a common axis of rotation, or in an opposite direction of rotation. A flow of air for promoting the mulching process is produced by the trailing edges of the knives and directed away from the plane of movement of the housing. This reference has not been capable of solving the problem of adequate, finely crushed mulching.
The knives proposed for sickle-type lawnmowers are expected to also produce, in combination with adequate mowing capacities, an efficient mulching of the cut, mowed material. The problem was designing the knife blades in an offset or stepped configuration, and to have these blades operate in several planes of rotation. The mowed material should also be lifted and possibly conveyed several times into the revolving knife blades depending on the degree of dryness or length of the grass. The result was that the mowed material is crushed a number of times. This is accomplished by providing wing-like guide surfaces mounted on the ends of the wings or knives set in a slanted manner.
The blades of the knives contain guide surfaces that are slanted with respect to the plane of rotation of the knife. Starting from the longitudinal leading edges of the knife blades, these blades extend in an ascending manner to the longitudinal trailing edges. Furthermore, the outer segment of the blades are contoured inward so that the segment is disposed below the plane of the hub part.
In addition, there are also repelling elements extending upwards and downwards at the ends of the blades in the direction of rotation behind the blades in the longitudinal direction of the knife. These repelling elements are attached perpendicular or inclined in relation to the plane of rotation of the knife. In addition, through different dimensioning of the active surfaces of these repelling elements effects of eddying are increased, and thus of multiple crushing of the mowed material.
Although it has been possible to make progress with these knives, the desired success has not been accomplished. The expected ejection of the cut material or its introduction into the soil of the mowed lawn still continues to be inadequate.
An object of the present invention is to provide a mowing and mulching system operating with lawnmowers that creates a finer mulching of the cut grass.
Another object is to provide a more completely operating mowing and mulching system that substantially improves the cutting capacity and the crushing of the mowed material to the finest degree. The system also ejects the mulched, almost pulverized cut grass in a targeted manner by pressing the latter into the grass sod and depositing it there.
The mowing and mulching system of the present invention operates as a combined system. The blades of the knives are arranged in a staggered manner next to each other and offset in relation to each other in the working direction. The blades are disposed in a common cutting plane. Thus, the outer segments of the cutting edges are disposed within the zone of the ends of the blades. Each edge is disposed below the plane of the hub part of the knife. The outer segment of the cutting edge is adjoined by a center cutting edge segment that is elevated beyond the plane of the hub part, and by an inner cutting edge segment that merges into the hub part and ends there. The ends of the blades of the knife, of which the longitudinal leading edges, viewed in the direction of rotation, are disposed below the plane of the hub part. These edges are in the form of baffle surfaces that are set slanted versus the plane of rotation of the knife. The baffle surfaces extend in an ascending manner, starting from the leading longitudinal edge to the longitudinal trailing edge, viewed in the direction of rotation.
This knife configuration is employed in a sickle-type lawnmower comprising a pot-like cover for receiving the knives. This cover is open at the bottom side and, viewed in the cutting direction, and comprises rear and side walls that reach up to below the plane of the outer segments of the blades.
The desired fine crushing process is accomplished, to obtain finely mulched, mowed material. The mowed material cut by the outer segments of the cutting edges of the knife blades and is repeatedly cut and crushed within the cover of the sickle-type lawnmower. For this purpose, the mowing gear having two or multi-bladed knives has a mulching mechanism that produces repeated cutting and crushing of the mowed material.
The mulching system is comprised of a dish-like turbo-disk fitted with baffle plates. The turbo-disk is disposed in the hub zone of the knife and secured on the driving shaft. The turbo-disk generates a turbo-effect so that the cut, mowed material is whirled around a number of times within the pot-like cover and seized several times by the knife blades and cut into small pieces. To create intensive whirling of the cut, mowed material within the cover, the system comprises a receiving dish. This receiving dish contains a plurality of baffle plates arranged in a radial manner or in the plane of a leading or trailing secant and projecting axially from the plane of the receiving dish. The received mowed material is continually whirled around by the baffle plates and repeatedly supplied in a crushing manner to the cutting planes of the knife, to be cut and crushed there again. A similar effect is obtained by the baffle surfaces or repelling elements arranged on the outer blade segments, which guide the mowed and mulched pieces of grass against the flow of the grass particles produced by the turbo-disk, so that further thorough mixing is achieved.
The baffle plates can be adjusted so that the mowed material such as the shape and size, are made available in different arrangements and forms of embodiments depending on whether the grass is, a leaf or stem type, or dry or moist.
Furthermore, a turbine designed like a type of bucket wheel creates an effective crushing and mulching. The turbine is arranged in the direction of motion of the lawnmower to the side of the staggered knife arrangement, preferably above the plane of rotation and cutting of said knives. The direction of rotation of the turbine corresponds with one of the knives, which are driven in the same direction of rotation.
The turbo-disks arranged on the axles of the individual knives may have different turbo-effects. The turbine generates turbulences within the pot-like cover for continuously whirling around the mowed material.
This system achieves a high degree of mulching of the mowed material along with good mowing capacity. This high degree of mulching is an important precondition to be satisfied for reintroducing the mowed material into the soil as green fertilizer.
The turbo-effect generated by the turbo-disks makes sure that the mulched material is pressed into the mowed surface of the lawn. The material does not have to be disposed of in some other way, as it is typically the case.